package challenge;

public class WhatString {
	
	public static void main(String args[]){
		String st = " ";
		System.out.println("st:"+st);
		st=st.concat("str");
		System.out.println("st:"+st);
		for(int i=0;i<10;i++){
			st = String.format("%03d", i+1);
			System.out.println("st:"+st);
		}
	}
}
